This invention relates to mass transfer packing elements, (sometimes called structured packing elements), and specifically to packing elements in the form of corrugated sheets of the kind provided in stacks with the lines of corrugation angled with respect to the sheets directly above and below.
Packing elements of the above kind are frequently used in mass transfer and heat transfer applications where the process requires that a liquid be placed in intimate contact with a counterflowing gas with a view to either extracting or entraining a component, reducing or increasing the temperature or facilitating a chemical reaction. In such cases the corrugated sheets generally define a plurality of pathways through which the liquid may pass as in transits the container in which the sheets are stacked, which is often a mass transfer tower. The liquid is constrained to flow in as thin a film as possible to maximize the surface area in contact with the gas.
The stacked corrugated sheets are typically located vertically with the lines of corrugations making an acute angle to the vertical with the angle being essentially constant in size but alternating to the left and right of the vertical in successive contacting sheets.
Providing a stack of sheets in such a fashion that the individual sheets will not become deformed or displaced in transit or in use has required that the sheets be fastened together in some fashion. This fastening also aids in the assembly and disassembly of the packing in the tower. Fastening has been done for example by driving one or more threaded screws through the stack of assembled elements. Alternatively one or more plain rods can be used with the exposed ends flattened to form a rivetted attachment. A further alternative comprises welding the sheets to one another at the points at which the corrugations contact one another.
Each of the above alternatives has its drawbacks. Screwing or rivetting can deform or skew the elements rendering them less efficient. In addition if, as is often the case, the elements have structural features such as indentations, perforations or reversals of the crests and valleys of the corrugations, these features may become distorted and ineffective. Welding the successive sheets can be difficult if the amplitude of the corrugations is small and the contacting area is likewise small. The chances of a misplaced spot weld is high and even well placed welds may be of such a small area that they are relatively weak.
The present invention provides a method of attaching a plurality of corrugated sheets that is very secure and easily carried out with minimal danger of any deformation of the sheets resulting therefrom. The process is adapted to be used with any design of corrugated sheet regardless of any structure imposed on the basic corrugated shape. It is therefore readily adapted to use wherever such tower packings are used.